Existing navigation displays provide a selectable indication of distance (or range) to reach a target altitude, which is known as the “range to altitude arc.” While this is a useful symbology for determining at which distance along the flight path a target altitude will be reached, it does not provide any time-related information.
Occasionally, Air Traffic Control (ATC) will issue a clearance that requires reaching an altitude within a certain amount of time. For example, ATC may issue commands such as “N1234, descend and maintain flight level two five zero. Be level at flight level two five zero in five minutes or less.” or “N1234, descend and maintain flight level two four zero. I need you out of flight level two seven zero in three minutes.” Today, upon hearing this type of clearance, a pilot will likely start an elapsed timer and initiate the descent by dialing in the target altitude and selecting a descent mode (e.g., vertical speed (VS) or flight path angle (FPA)). Once started down, the pilot must manually (e.g., by mental math) determine the descent rate required to reach the cleared altitude in time.
Having to manually determine the required descent rate increases pilot workload and can result in errors and/or violation of an ATC clearance. For example, a target altitude may not be reached in time due to a mental math error by the pilot. In some cases to avoid violating the clearance, a pilot may descend at a faster rate than required, potentially at an uncomfortable rate for the passengers. To avoid potential errors, pilot distraction, and/or passenger discomfort, there is a need in the art for improved methods of displaying time and range to altitude information.